Air Tunnel or rear discharge?

[agood]

I spoke with a local dealer this week about a new finish mower and he suggested the air tunnel design. I thought I wanted it a rear discharge but he said they do not cut well in damp grass and will leave rows of cut grass behind them. He suggested an air tunnel mower.
I need to mow a nice clean path.
What experiences have are here with the air tunnel design?
Thanks

 

[CTyler]

I am familiar with side and rear discharge but what is an air tunnel design?

 

[HayDR]

Sounds like a LandPride dealer wants to unload some old stock. The Air Tunnel is better than old conventional side discharge mowers but not as good as well designed rear discharge mower like a Midwest finish mower.

 

[BobinCols]

I can not comment on the air tunnel mower. I have seen them on Landpride's website and brochure. I have a RD7200 Woods rear discharge mower and it does a fine job of mowing our 5 acres of yard. We cut our grass twice a week if we have to in the spring. We never let it get over 4" tall. With what I said, there is no clumping and discharges nicely out the rear evenly. You can mow in any direction. The blade tip speed on this mower is like 17,000 rpm's.. It is very quiet-the only thing you hear is the air noise of the blades. This mower replaced a Woods RM306 side discharge mower which was not an air tunnel. I would never purchase a side discharge mower again.

 

[Junkman]

could you explain the principals of how a rear discharge mower works as opposed to how the side discharge mower works? I often wondered how the mower deck design was done to determine where the clippings will exit....

 

[JimMc]

Look at it from a standpoint of airflow management. Mower decks are ducted, vented, and shielded to cause the air to flow out the discharge.

Side discharge traditionally caused problems since the blade closest to the discharge had to process the clippings from other blades. This caused early dulling of the rightmost blade, streaking, clumping and a variety of other problems. Early attempts at solving this included speeding up the right blades, increasing the size of the right blade, etc.

The air tunnel concept as implemented by Land Pride, et. al. used shielding to essentially provide a duct for the clippings from the left most blades to bypass the right side blades, around the front and over, to reduce this additional work by the center and right blades. I say reduce because there must be some blade overlap to prevent streaking, so there is not a complete seal and separation of the blades and the resultant clippings. It is interesting to note that the newer ZTR's use a similar system, except that the clippings pass behind the blades. Interesting, because it solves the major problem of the front bypass system where the clippings must pass over the uncut grass rather than over the already cut grass. This probably wasn't as necessary until the advent of the ZTR and higher speeds of travel they brought on.

Rear discharge allows each blade to process it's own clippings and exhaust it behind and into the cut area. Typically, shielding is utilized to promote the exhaust of air and thereby clippings to the rear of the deck.

All this assumes you mow in a forward direction. /forums/images/graemlins/grin.gif Sorry to jump in here CCI, but I've been sort of "living" in this discussion for the past year. /forums/images/graemlins/tongue.gif

 

[agood]

</font><font color="blue" class="small">( Sounds like a LandPride dealer wants to unload some old stock. The Air Tunnel is better than old conventional side discharge mowers but not as good as well designed rear discharge mower like a Midwest finish mower. )</font>

Actually it is a bush hog model ATH720 and so far every dealer I have talked with in my area says this is the best finish mower on the market.....even one that did not sell Bush Hog. But I would prefer to hear testimonials on them from someone that actually uses it.....

What about First Choice Mowers.....I can get them fairly cheap from the dealer in NC everyone talks about...can't remember the name right now....
THanks

 

[agood]

</font><font color="blue" class="small">( I am familiar with side and rear discharge but what is an air tunnel design? )</font>

Here is the link to the Bush Hog Air Tunnel Mower:
http://www.bushhog.com/agtoc.html

 

[agood]

Jim,
Does the shape of the deck make any difference. I have seen seveal with square corners, like the Bush Hog and the Landpride 1560 I have now.....but some have rounded corners like First Choice. How would these designs effect the discharge of the clippings?

 

[JimMc]

Flip them over and look at the way the deflectors operate from underneath. Some square cornered mowers actually have circular shields underneath and mow quite a bit better than it would appear from the top. Those that don't will eventually accumulate a lot of packed clippings in those square corners. While they will mow better after the grass "grows" there because of the improved airflow, they will also begin to rust out in those areas due to trapped moisture. While looking don't forget the direction of blade rotation will appear as the opposite from when viewed from above. Just use the sharp edge of the blade to re-orient yourself, then just think like a cut piece of grass and see which direction you would go. /forums/images/graemlins/grin.gif